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22 August 2025
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Featured FRI Magazine article: Fire service response to incidents involving acetylene cylinders by Etienne du Toit
Acetylene van explosion research was carried out into how ventilation in the rear of enclosed vans affects the build-up of acetylene gas by the Health and Safety Laboratory, UK
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Acetylene presents a problem to fire fighters because it is found in every community
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A fire caused by ruptured acetylene tank in the USA. Inside were several thousand rounds of live ammunition, recreational vehicles and acetylene tanks
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Oxy-acetylene cylinders leaked then ignited in the back of a van
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https://www.frimedia.org/uploads/1/2/2/7/122743954/fri_vol_3_no_8.pdf
This week’s featured Fire and Rescue International magazine article is: Fire service response to incidents involving acetylene cylinders written by Etienne du Toit, deputy director: Fire Brigade Services, Western Cape Government (FRI Vol 3 no 8). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Fire service response to incidents involving acetylene cylinders
By Etienne du Toit, Deputy Director: Fire Brigade Services, Western Cape Government
This article is aimed at trained fire fighters with the necessary training, experience and equipment that may require additional background on dealing with acetylene cylinder emergencies. It is not intended for non-emergency responders and should not be seen to replace any standard operating procedure (SOP) or material safety data sheet (MSDS).
The 2015 Tianjin explosions were a series of explosions that occurred at a container storage station at the Port of Tianjin starting on Wednesday, 12 August 2015. The first two explosions occurred within 30 seconds of each other at the facility, which is located in the Binhai New Area of Tianjin, China. Over one hundred people were killed and hundreds of others were injured.
It has not yet been determined what chemicals were being stored at the site. In addition to vast quantities of sodium cyanide and calcium carbide, 800 tons of ammonium nitrate and 500 tons of potassium nitrate were found, according to local reports. On 17 August 2015, the deputy director of the public security bureau's fire department told CCTV, “Over 40 kinds of hazardous chemicals (were stored on site). As far as we know, there were ammonium nitrate and potassium nitrate. According to what we know so far, all together there should have been around 3 000 tons.”
Ammonium nitrate, which is principally used in manufacturing fertiliser and the production of explosives, has been implicated in a number of other fatal industrial explosions. A fire department spokesman confirmed that fire fighters had used water in combating the initial fire, which may have led to water being sprayed on calcium carbide, releasing the highly volatile gas, acetylene. This may have ignited, detonating the ammonium nitrate. In subsequent discussions it became evident that there is a general lack of understanding as far as acetylene is concerned. In South Africa, calcium carbide is transported in sealed containers with a water tight nitrogen blanket.
The prevalence of acetylene makes it one of the more common cylinder responses. Sometimes the cylinder is merely leaking without any fire and sometimes the gas leaking from the cylinder may have ignited. It is not unusual to find acetylene cylinders abandoned or dumped in vacant commercial and industrial facilities or even open veld. Abandoned cylinders have also been found at rubbish dumps and metal recyclers.
Fire service emergency response involving compressed gas cylinders are among the most potentially destructive and life threatening. Leaking and burning cylinders may contain one of many different gases, pure or in mixtures that can cause serious injury in numerous ways. Compounding the problem is that there seems to be a lack of readily available information for responders on how to handle compressed gas cylinders. Most safety data sheets (SDSs), formerly referred to as MSDSs and guideline documents, will normally require the notification of the fire and rescue services, however, very little information is readily available to these agencies.
Acetylene, when stored as a compressed gas in a cylinder, is unique in its ability to continue to ‘self-heat’ after the fire has been extinguished. When involved in a fire, acetylene can begin to decompose once a temperature of 300 degrees Celsius is reached; that is, break down into its constituent elements of hydrogen and carbon. The decomposition reaction is exothermic; that is, it produces heat. Acetylene cylinders are designed to contain and inhibit decomposition; however, if left unchecked, decomposition could lead to the failure of the cylinder. This means that unlike other fuel gases, acetylene may continue to be a hazard after the fire has been extinguished and requires specific operational procedures.
This article examines fire service response to emergencies involving acetylene, focussing on the following scenarios:
Characteristics of acetylene
Acetylene (C2H2) is not an air gas but a synthesis gas generally produced from the reaction of calcium carbide with water. A gaseous hydrocarbon, it is colourless, has a strong garlic odour, is unstable, highly combustible and produces a very hot flame (over 3 000 degrees Celsius) when combined with oxygen.
Acetylene presents a problem to fire fighters because it is found in every community, ranging from large industrial plants to ‘roadside’ exhaust repair in an informal settlement. These environments may range from extremely well regulated to totally uncontrolled.
Product identification
One of the primary objectives during the response phase of any incident involving hazardous materials is the identification of the product involved. The shape of a container may be used to identify the type of chemical involved. A cylinder made for low-pressure, liquefied compressed gas service generally has broad and fat proportions. Dissolved acetylene cylinders are predominantly used in South Africa and similar to the permanent gas cylinders. A high-pressure cylinder containing a compressed gas (one that is nonliquefied, called a permanent gas) is relatively taller and thinner and more bullet shaped.
Acetylene cylinders are maroon in colour in accordance with South African National Standards (SANS) 10019. For acetylene being transported, examining the shipping papers, dangerous goods declaration (DGD), transport emergency card (TREMCARD) and manifest are definitive methods of identification. The manifest should list the number of the full and empty cylinders being carried and generally occurs at the beginning and end of the delivery process.
For cylinders containing flammable and non-flammable gases transported by private or contract carriers, a colour-coded SANS compliant label must be used. The use of the Department of Transport (DoT) label, as sometimes taught in South African hazardous material (hazmat) training, may not be used.
Such cylinders may have a welded seam running either the length or the circumference of the container and usually there is a foot ring at the base. The cylinder will have fusible-plug type pressure relief devices. These devices are designed to melt when their temperature reaches about 107 degrees Celsius (ISO 3807Annex G). When a fusible plug is activated, the entire content is expelled. There will be at least one such device at the top of the cylinder, either as part of the valve assembly or adjacent to it. Additionally, there will also be a fusible plug at the bottom. Although this will vary with the size of the cylinder, this is the basic arrangement.
It is important to note that acetylene being dissolved in the liquid acetone, which is held in porous material, can result in some strange effects during use for cutting and welding.
When an acetylene cylinder is transported horizontally, the acetone will slowly redistribute in a horizontal manner. If the cylinder is placed vertically again, it will take a long time before the acetone is back in the position in which it is intended to be. The result is that if used immediately after having been stored in a horizontal plane, liquid acetone comes out with the gas flow of acetylene in the torch. This can have a dramatic influence on the torch flame; it becomes very unstable. This is often referred to as ‘spitting’ as it looks like spitting. If a cylinder has been transported or stored horizontally, you should wait at least two days after placing the cylinders in its normal vertical position before using them.
Leaking cylinders
Always consider the Safety Data Sheet (SDS) and all available information to guide your actions.
A leaking cylinder without a fire is dangerous because the gas could find an ignition source and explode ie unconfirmed vapour cloud explosion (UVCE). If an acetylene cylinder is suspected of leaking, check it to determine if this is the case and place a hose line in position to hydraulically ventilate the escaping gas. When checking for leaks, take care when using a combustible gas detector. Acetylene gas burns so hot it can burn out the catalytic filament in the bridge, thus destroying the sensor. Also, the fumes of burning acetylene may coat the filament in the bridge, which may reduce the instrument`s accuracy for future readings. Always follow the manufacturer’s instructions when using any detection devices regardless of make and application. Based on the various methods of identification, we should know what the product is. We know that acetylene is flammable therefore there is no reason to use a gas detector to detect a leak. A simple soap-and-water solution will effectively determine the location of the leak.
Typical leak points are the packing nut, the valve threads, the regulator and other attachments. Fusible plugs, if fitted, should also be inspected. Tighten attachments from which acetylene is leaking. Remember that the regulator connection is a left-handed thread and must be turned anti-clockwise to be tightened. Acetylene cylinders are normally equipped with a packing valve. If the leak emanates from the valve stem, try shutting the valve and tightening the packing nut under the valve handle. This compresses the packing material and should stop the leak. If the valve continues to leak, move the cylinder to an open outside area and allow the gas to slowly vent until the cylinder empties. The area should be monitored, and a hose line should be used to dissipate the gas. Never over pack a leaking acetylene cylinder into any type of containment or over drum type device. If a leaking cylinder is over packed, the pure acetylene released will become pressurised inside the containment device and may spontaneously ignite as the pressure rises above 150kPa. Under these circumstances, the cylinder should be moved to a safe area and be allowed to depressurise before any repairs are attempted.
Fire situations involving acetylene cylinders
Again, all actions taken must be in accordance with the standard operating procedures or guidelines of the relevant fire service, MSDS or Emergency Response Guidebook.
The United Kingdom Department of Communities and Local Government’s Chief Fire and Rescue Advisor’s “Operational guidance for incidents Involving hazardous materials” is an excellent publication and describe detailed actions to be followed: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/15082/GRA_Hazmat_Manual_part_1.pdf.
If no positive identification is possible, rather treat any cylinder involved as acetylene. Evacuation, the creation of an exclusion zone and the deployment of hose lines for cooling and exposure protection should form part the initial tactical objectives. It is also extremely important that the cylinder agent be notified of the incident as early as possible.
Fires involving acetylene cylinders have various causes and may involve cylinders and hoses during welding and cutting operations. The heat may in certain cases cause the fusible plug to melt, resulting in a fire that vents from the fusible plug opening. This may sometimes be referred to as an ‘explosion’ due to the sudden and very high pitched noise, the former is in fact not an explosion but rather an energy release. Depending on the cylinder`s internal pressure, the flames can reach two to three metres into the air. As the gas burns off, the pressure inside the cylinder drops and the size of the flame will diminish accordingly. In this situation, it is important to get water from a hose line on the cylinder in order to cool it and also protect any exposures. This is best done from a position of safety; for example, by shielding from ‘behind heavy machinery or a solid wall’. A fixed water monitor could be used for this. A coarse water spray giving wide application cover is preferable to a jet. Always bear in mind that the cylinder has fusible plugs; if the cylinder heats up and water is keeping just the plugs cool, the plugs may not function and the cylinder may rupture. Always be aware of other cylinders in the vicinity that may create an exposure problem. Move those if safe to do so, if not safe also cool them.
Do not attempt to move a burning cylinder; it is dangerous to do so. Decide whether to allow the cylinder to burn whilst being cooled or to extinguish the fire and plug the leak.
Take note that these procedures are to be undertaken by the fire service. Individual incident commanders may decide to change their tactics according to the circumstances of the incident. This procedure may contradict the generally accepted principle of never overriding a pressure-release device; the reasons for doing this may be sound being informed by the situation at hand.
If allowed to vent, there is always the possibility that a flammable mixture may form and ignite. It could take a substantial amount of time to empty a cylinder, depending on its pressure and the size of the leak. Fire fighters may be tied up for substantial period while venting and monitoring the situation. Remember, there is more than one fusible plug on a cylinder. Despite one being plugged, the remaining ones can still activate should a secondary problem occur. This procedure may be regarded as being safe provided that the cylinder is promptly handed over to the owner company.
A fire from a leaking valve stem may also occur. One method of handling this situation is to extinguish the fire and then treat the cylinder the same as any other leaking cylinder. However, if such a fire is extinguished, there is always the possibility that tightening the packing material will not stop the leak. In this case, the product will continue to release and must be vented with the area monitored for any accumulation of gas.
Another possible scenario is the decomposition of the acetylene inside the cylinder, which is accompanied by an exothermic reaction. This may be the result of the cylinder’s exposure to heat, even very briefly, such as a welder`s torch, flashback or a nearby fire. This may be recognised through discolouration, an area on the cylinder that is hot to touch or dries faster than the rest even after the application of water. It has also been reported that in severe cases bulging have occurred on the affected area of the cylinder. A thermal imaging camera (TIC) may also reveal hot areas. Close the valve of such a cylinder. This will prevent more acetylene from being drawn to the hot spot inside and the reaction should eventually cease. The heat given off by the decomposition is dissipated to the outside wall and is conducted away by the matrix inside. However, in this situation, the cylinder should be kept cool by water from a hose line or through immersion in water. The cylinder must be monitored until the decomposition ceases after the valve is closed.
How long must the cylinder be cooled to ensure any acetylene decomposition is over and cannot re-start?
The German Federal Institute for Materials Research and Testing (BAM) has performed extensive research into acetylene cylinder decomposition.
For more information from BAM visit their website: http://www.bam.de/en/kompetenzen/fachabteilungen/abteilung_2/fg21/index.htm
Necessity
Gas storage cylinders potentially pose a major problem for fire and emergency services. Close liaison with suppliers and manufacturers is recommended; these companies have vast experience and are valuable sources of information. Obtain Gas Association pamphlets, South African National Standards (SANS) and industry safety information to learn more. Safety material from gas suppliers contains information on cylinders and their contents and reports on incidents, how they have caused death and destruction. Know what you are dealing with and constantly train and update emergency response procedures.
References
This week’s featured Fire and Rescue International magazine article is: Fire service response to incidents involving acetylene cylinders written by Etienne du Toit, deputy director: Fire Brigade Services, Western Cape Government (FRI Vol 3 no 8). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Fire service response to incidents involving acetylene cylinders
By Etienne du Toit, Deputy Director: Fire Brigade Services, Western Cape Government
This article is aimed at trained fire fighters with the necessary training, experience and equipment that may require additional background on dealing with acetylene cylinder emergencies. It is not intended for non-emergency responders and should not be seen to replace any standard operating procedure (SOP) or material safety data sheet (MSDS).
The 2015 Tianjin explosions were a series of explosions that occurred at a container storage station at the Port of Tianjin starting on Wednesday, 12 August 2015. The first two explosions occurred within 30 seconds of each other at the facility, which is located in the Binhai New Area of Tianjin, China. Over one hundred people were killed and hundreds of others were injured.
It has not yet been determined what chemicals were being stored at the site. In addition to vast quantities of sodium cyanide and calcium carbide, 800 tons of ammonium nitrate and 500 tons of potassium nitrate were found, according to local reports. On 17 August 2015, the deputy director of the public security bureau's fire department told CCTV, “Over 40 kinds of hazardous chemicals (were stored on site). As far as we know, there were ammonium nitrate and potassium nitrate. According to what we know so far, all together there should have been around 3 000 tons.”
Ammonium nitrate, which is principally used in manufacturing fertiliser and the production of explosives, has been implicated in a number of other fatal industrial explosions. A fire department spokesman confirmed that fire fighters had used water in combating the initial fire, which may have led to water being sprayed on calcium carbide, releasing the highly volatile gas, acetylene. This may have ignited, detonating the ammonium nitrate. In subsequent discussions it became evident that there is a general lack of understanding as far as acetylene is concerned. In South Africa, calcium carbide is transported in sealed containers with a water tight nitrogen blanket.
The prevalence of acetylene makes it one of the more common cylinder responses. Sometimes the cylinder is merely leaking without any fire and sometimes the gas leaking from the cylinder may have ignited. It is not unusual to find acetylene cylinders abandoned or dumped in vacant commercial and industrial facilities or even open veld. Abandoned cylinders have also been found at rubbish dumps and metal recyclers.
Fire service emergency response involving compressed gas cylinders are among the most potentially destructive and life threatening. Leaking and burning cylinders may contain one of many different gases, pure or in mixtures that can cause serious injury in numerous ways. Compounding the problem is that there seems to be a lack of readily available information for responders on how to handle compressed gas cylinders. Most safety data sheets (SDSs), formerly referred to as MSDSs and guideline documents, will normally require the notification of the fire and rescue services, however, very little information is readily available to these agencies.
Acetylene, when stored as a compressed gas in a cylinder, is unique in its ability to continue to ‘self-heat’ after the fire has been extinguished. When involved in a fire, acetylene can begin to decompose once a temperature of 300 degrees Celsius is reached; that is, break down into its constituent elements of hydrogen and carbon. The decomposition reaction is exothermic; that is, it produces heat. Acetylene cylinders are designed to contain and inhibit decomposition; however, if left unchecked, decomposition could lead to the failure of the cylinder. This means that unlike other fuel gases, acetylene may continue to be a hazard after the fire has been extinguished and requires specific operational procedures.
This article examines fire service response to emergencies involving acetylene, focussing on the following scenarios:
- Leaking cylinders without ignition of gas
- Cylinders involved in fire
Characteristics of acetylene
Acetylene (C2H2) is not an air gas but a synthesis gas generally produced from the reaction of calcium carbide with water. A gaseous hydrocarbon, it is colourless, has a strong garlic odour, is unstable, highly combustible and produces a very hot flame (over 3 000 degrees Celsius) when combined with oxygen.
- Major hazard: fire
- Toxicity: simple asphyxiant
- Flammability limits in air ie standard temperature and pressure (STP) conditions: 2.4-83 volume percent (The upper limit could reach 100 percent)
- Odour: garlic-Like
- UN Number: UN 1001
- Hazard class : Class 2: Division 2.1 flammable gas
Acetylene presents a problem to fire fighters because it is found in every community, ranging from large industrial plants to ‘roadside’ exhaust repair in an informal settlement. These environments may range from extremely well regulated to totally uncontrolled.
Product identification
One of the primary objectives during the response phase of any incident involving hazardous materials is the identification of the product involved. The shape of a container may be used to identify the type of chemical involved. A cylinder made for low-pressure, liquefied compressed gas service generally has broad and fat proportions. Dissolved acetylene cylinders are predominantly used in South Africa and similar to the permanent gas cylinders. A high-pressure cylinder containing a compressed gas (one that is nonliquefied, called a permanent gas) is relatively taller and thinner and more bullet shaped.
Acetylene cylinders are maroon in colour in accordance with South African National Standards (SANS) 10019. For acetylene being transported, examining the shipping papers, dangerous goods declaration (DGD), transport emergency card (TREMCARD) and manifest are definitive methods of identification. The manifest should list the number of the full and empty cylinders being carried and generally occurs at the beginning and end of the delivery process.
For cylinders containing flammable and non-flammable gases transported by private or contract carriers, a colour-coded SANS compliant label must be used. The use of the Department of Transport (DoT) label, as sometimes taught in South African hazardous material (hazmat) training, may not be used.
Such cylinders may have a welded seam running either the length or the circumference of the container and usually there is a foot ring at the base. The cylinder will have fusible-plug type pressure relief devices. These devices are designed to melt when their temperature reaches about 107 degrees Celsius (ISO 3807Annex G). When a fusible plug is activated, the entire content is expelled. There will be at least one such device at the top of the cylinder, either as part of the valve assembly or adjacent to it. Additionally, there will also be a fusible plug at the bottom. Although this will vary with the size of the cylinder, this is the basic arrangement.
It is important to note that acetylene being dissolved in the liquid acetone, which is held in porous material, can result in some strange effects during use for cutting and welding.
When an acetylene cylinder is transported horizontally, the acetone will slowly redistribute in a horizontal manner. If the cylinder is placed vertically again, it will take a long time before the acetone is back in the position in which it is intended to be. The result is that if used immediately after having been stored in a horizontal plane, liquid acetone comes out with the gas flow of acetylene in the torch. This can have a dramatic influence on the torch flame; it becomes very unstable. This is often referred to as ‘spitting’ as it looks like spitting. If a cylinder has been transported or stored horizontally, you should wait at least two days after placing the cylinders in its normal vertical position before using them.
Leaking cylinders
Always consider the Safety Data Sheet (SDS) and all available information to guide your actions.
A leaking cylinder without a fire is dangerous because the gas could find an ignition source and explode ie unconfirmed vapour cloud explosion (UVCE). If an acetylene cylinder is suspected of leaking, check it to determine if this is the case and place a hose line in position to hydraulically ventilate the escaping gas. When checking for leaks, take care when using a combustible gas detector. Acetylene gas burns so hot it can burn out the catalytic filament in the bridge, thus destroying the sensor. Also, the fumes of burning acetylene may coat the filament in the bridge, which may reduce the instrument`s accuracy for future readings. Always follow the manufacturer’s instructions when using any detection devices regardless of make and application. Based on the various methods of identification, we should know what the product is. We know that acetylene is flammable therefore there is no reason to use a gas detector to detect a leak. A simple soap-and-water solution will effectively determine the location of the leak.
Typical leak points are the packing nut, the valve threads, the regulator and other attachments. Fusible plugs, if fitted, should also be inspected. Tighten attachments from which acetylene is leaking. Remember that the regulator connection is a left-handed thread and must be turned anti-clockwise to be tightened. Acetylene cylinders are normally equipped with a packing valve. If the leak emanates from the valve stem, try shutting the valve and tightening the packing nut under the valve handle. This compresses the packing material and should stop the leak. If the valve continues to leak, move the cylinder to an open outside area and allow the gas to slowly vent until the cylinder empties. The area should be monitored, and a hose line should be used to dissipate the gas. Never over pack a leaking acetylene cylinder into any type of containment or over drum type device. If a leaking cylinder is over packed, the pure acetylene released will become pressurised inside the containment device and may spontaneously ignite as the pressure rises above 150kPa. Under these circumstances, the cylinder should be moved to a safe area and be allowed to depressurise before any repairs are attempted.
Fire situations involving acetylene cylinders
Again, all actions taken must be in accordance with the standard operating procedures or guidelines of the relevant fire service, MSDS or Emergency Response Guidebook.
The United Kingdom Department of Communities and Local Government’s Chief Fire and Rescue Advisor’s “Operational guidance for incidents Involving hazardous materials” is an excellent publication and describe detailed actions to be followed: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/15082/GRA_Hazmat_Manual_part_1.pdf.
If no positive identification is possible, rather treat any cylinder involved as acetylene. Evacuation, the creation of an exclusion zone and the deployment of hose lines for cooling and exposure protection should form part the initial tactical objectives. It is also extremely important that the cylinder agent be notified of the incident as early as possible.
Fires involving acetylene cylinders have various causes and may involve cylinders and hoses during welding and cutting operations. The heat may in certain cases cause the fusible plug to melt, resulting in a fire that vents from the fusible plug opening. This may sometimes be referred to as an ‘explosion’ due to the sudden and very high pitched noise, the former is in fact not an explosion but rather an energy release. Depending on the cylinder`s internal pressure, the flames can reach two to three metres into the air. As the gas burns off, the pressure inside the cylinder drops and the size of the flame will diminish accordingly. In this situation, it is important to get water from a hose line on the cylinder in order to cool it and also protect any exposures. This is best done from a position of safety; for example, by shielding from ‘behind heavy machinery or a solid wall’. A fixed water monitor could be used for this. A coarse water spray giving wide application cover is preferable to a jet. Always bear in mind that the cylinder has fusible plugs; if the cylinder heats up and water is keeping just the plugs cool, the plugs may not function and the cylinder may rupture. Always be aware of other cylinders in the vicinity that may create an exposure problem. Move those if safe to do so, if not safe also cool them.
Do not attempt to move a burning cylinder; it is dangerous to do so. Decide whether to allow the cylinder to burn whilst being cooled or to extinguish the fire and plug the leak.
Take note that these procedures are to be undertaken by the fire service. Individual incident commanders may decide to change their tactics according to the circumstances of the incident. This procedure may contradict the generally accepted principle of never overriding a pressure-release device; the reasons for doing this may be sound being informed by the situation at hand.
If allowed to vent, there is always the possibility that a flammable mixture may form and ignite. It could take a substantial amount of time to empty a cylinder, depending on its pressure and the size of the leak. Fire fighters may be tied up for substantial period while venting and monitoring the situation. Remember, there is more than one fusible plug on a cylinder. Despite one being plugged, the remaining ones can still activate should a secondary problem occur. This procedure may be regarded as being safe provided that the cylinder is promptly handed over to the owner company.
A fire from a leaking valve stem may also occur. One method of handling this situation is to extinguish the fire and then treat the cylinder the same as any other leaking cylinder. However, if such a fire is extinguished, there is always the possibility that tightening the packing material will not stop the leak. In this case, the product will continue to release and must be vented with the area monitored for any accumulation of gas.
Another possible scenario is the decomposition of the acetylene inside the cylinder, which is accompanied by an exothermic reaction. This may be the result of the cylinder’s exposure to heat, even very briefly, such as a welder`s torch, flashback or a nearby fire. This may be recognised through discolouration, an area on the cylinder that is hot to touch or dries faster than the rest even after the application of water. It has also been reported that in severe cases bulging have occurred on the affected area of the cylinder. A thermal imaging camera (TIC) may also reveal hot areas. Close the valve of such a cylinder. This will prevent more acetylene from being drawn to the hot spot inside and the reaction should eventually cease. The heat given off by the decomposition is dissipated to the outside wall and is conducted away by the matrix inside. However, in this situation, the cylinder should be kept cool by water from a hose line or through immersion in water. The cylinder must be monitored until the decomposition ceases after the valve is closed.
How long must the cylinder be cooled to ensure any acetylene decomposition is over and cannot re-start?
- Acetylene cylinders involved in fires become safe and stable after just one hour cooling. In addition one hour monitoring time has been added to double the known safety margin.
- When effective cooling of the cylinder shell has been achieved, water cooling should be stopped. The cylinder should still not be moved for a further one hour and an appropriate, risk assessed hazard zone should be maintained. This monitoring phase is required due to the possibility of internal decomposition occurring.
The German Federal Institute for Materials Research and Testing (BAM) has performed extensive research into acetylene cylinder decomposition.
For more information from BAM visit their website: http://www.bam.de/en/kompetenzen/fachabteilungen/abteilung_2/fg21/index.htm
Necessity
Gas storage cylinders potentially pose a major problem for fire and emergency services. Close liaison with suppliers and manufacturers is recommended; these companies have vast experience and are valuable sources of information. Obtain Gas Association pamphlets, South African National Standards (SANS) and industry safety information to learn more. Safety material from gas suppliers contains information on cylinders and their contents and reports on incidents, how they have caused death and destruction. Know what you are dealing with and constantly train and update emergency response procedures.
References
- http://encyclopedia.airliquide.com/
- http://www.newworldencyclopedia.org/entry/Acetylene
- ANSI/NFPA 51B, Fire prevention in use of cutting and welding processes.
- SANS 220, Dissolved acetylene cylinders.
- SANS 3821/ISO 3821, Gas welding equipment - Rubber hoses for welding, cutting and allied processes.
- SANS 10019, Transportable containers for compressed, dissolved and liquefied gases – Basic design, manufacture, use and maintenance.
- http://www.bam.de/en/kompetenzen/fachabteilungen/abteilung_2/fg21/index.htm
- https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/15082/GRA_Hazmat_Manual_part_1.pdf
- https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/15083/GRA_Hazmat_Manual_part_2.
- British Compressed Gases Association (www.BCGA.co.uk)-Cylinders in Fires Customer Leaflet: L6, ISSUE 2/ 2008
- European Industrial Gases Association AISBL: Doc 123/13 Code of Practice: Acetylene
- Wilhelmsen Ships Service entitled, “Understanding Acetylene”